The present invention relates to rotor provided with bearing trunnions, which rotor is made of lightweight material having limited strength properties.
When rotors are made of a material with limited strength properties in comparison to steel, some problems are involved in the provision of the bearing trunnions. If the bearing trunnions are made of the same material as the rotors and integrated with the rotors, e.g. of aluminum, magnesium, plastics or ceramic material, the bearing trunnions will get an unpractically large diameter and so also the bearings. This disadvantage is particularly obvious at journalling of the low pressure ends of the rotors in screw compressors provided with axial inlet ports, the design of which is restricted by bearing trunnions and bearings having a large diameter. The provision of axially positioned screws for reinforcing the bearing trunnions has been tested, but this has not been sufficient for avoiding harmful flexural stresses to the bearing trunnions. Steel shafts passing through especially plastic rotors have been used, resulting in sufficient bending strength, but at the same time resulting in an increased rotor weight where low weight is desired.
The object of the present invention is to achieve in a simple way rotors having bearing trunnions which have a comparatively small diameter but at the same time a great strength property, especially bending strength.